1. Field Of The Invention
This invention relates to the lifting blades of helicopters, more specifically to methods for folding the blades of the main rotor for purposes of storage.
2. Summary Of The Prior Art
In the prior art, the main rotor blades of helicopters are constructed to permit folding of the blade about the rotor to decrease the space required for storing the aircraft. In addition to conservation of storage space, the folded blades generally are secured to prevent damage caused by the blades striking each other in high winds or other conditions that cause movement of the blades.
Many of these prior art systems are comprised of motors, gears, linkages and control systems that automatically fold the main rotor blades of the helicopter. U.S. Pat. Nos. 4,376,979, 4,354,234, 3,749,515, 3,743,441, 3,484,175, and 3,356,155 all show motorized, fully automated blade folding systems. Such systems add a great deal of weight to the helicopter, and are difficult to maintain and inspect.
Other prior art blade folding systems are completely manual in operation. U.S. Pat. No. 4,712,978 shows one such method and apparatus. U.S. Pat. Nos. 4,623,300 and 4,252,504 show main rotor blade supports and locking member systems, respectively, adapted for use in manual blade folding systems. In these prior art rotor blade folding systems, workers are required to move the blades manually from the ground using a crutch pole or other device. When the locking member is released, the blade and rotor structure loses a great deal of rigidity. If a person moving the blades manually were to drop the blade with the locking member released, serious damage to the hinge pin, the yoke, or the blade itself is quite possible. To avoid such damage, in one prior art technique supporting braces are secured to the rotor assembly during the folding process. This procedure is time-consuming and requires heavy and cumbersome ground support equipment.